Microstructures and mechanical properties of hot-pressed MoSi2-matrix composites reinforced with SiC and ZrO2 particles

MoSi2-matrix composites reinforced with ZrO2 and SiC particles were fabrica ted by means of combustion synthesis (CS) combined with high-energy mechani cal milling (MM) and hot-pressing and sintering. The microstructures and me chanical properties of the composites were investigated by X-ray diffractom etry (XRD), scanning and transmission electron microscopy (SEM and TEM), an d with a universal materials testing machine. The results show that SIC par ticles are mainly distributed inside the grains of the MoSi2 matrix, while ZrO2 particles are distributed at the inter-granular region and produce coa lesence and coarsening of the matrix grains during hot pressing. The room-t emperature indentation fracture toughness of the composites reinforced with ZrO2 particles non-stabilized by Y2O3 (the reinforcing agent is coded as O Y-PSZ) was higher than that of the composites reinforced with ZrO2 particle s stabilized by 2.5 mol% Y2O3 (the reinforcing agent is coded as 2.5Y-PSZ). However, the latter show higher bend strengths. Moreover, the composites h ot-pressed at 1400 degreesC has a lower bend strength than hot-pressed mono lithic MoSi2. It is obvious that there is a synergistic effect of SiC and Z rO2 on the mechanical properties of ZrO2(MoSi2 + SiC) composites. (C) 2001 Elsevier Science Ltd. All rights reserved.